Air conditioning installations are already known which include an evaporator which is adapted for a stream of air to be treated to pass through it, and to cool the said air stream and extract the humidity from it, with formation of a condensate, the installation further including a heating device for heating the cooled air stream as required, so as to provide a stream of treated air for delivery into the cabin of the vehicle. Such an installation will be referred to herein as an installation of the kind specified.
An installation of this kind is known in particular from French patent application No. 80-23807, published under the number 2 469 304, in which means are also provided for preventing icing of the evaporator, while allowing it to operate at its maximum refrigerating capacity. In known installations of that type, a stream of cooled air is obtained at the outlet of the evaporator. The humidity of this cooled air stream depends on its temperature, i.e. the lower the temperature the lower the humidity. Humidity which is thus extracted from the air stream as it passes through the evaporator forms a condensate which is simply evacuated below the vehicle. The cooled air stream, having a low humidity, then passes through the heating device, so as to bring it to the desired temperature. However, its humidity remains unchanged.
In such known installations, the evaporator is part of the refrigeration circuit through which a refrigerant fluid circulates. The refrigerant circuit also includes a condenser. The heating device commonly consists of a heat exchanger through which the engine cooling fluid of the vehicle circulates. As the evaporator operates at its maximum refrigerating capacity, it follows that the stream of treated air has a very low humidity regardless of its temperature, since regulation of its temperature does not change its degree of humidity.
Such known installations therefore have the major drawback of producing a stream of treated air the humidity of which is not only much too low, but cannot be adjusted at will.